Contemporary computing devices allow users to input information in a number of ways, including via a keyboard, by or more types of pointing devices, and dedicated hardware buttons (typically on portable devices). With respect to pointing devices, a computer system may receive user input from a mouse and/or a touchpad, and if configured with a digitizer, by sensing pen and touch data, e.g., entered via a stylus (pen) or a finger.
Some personal computers, such as tablet-based personal computers, have the digitizer built into the display screen. This is highly beneficial for many users, because such a computing device can be operated with or without a keyboard. Tablet-based personal computers and similar handwriting-receptive computing devices allow users to enter handwritten data such as printed characters and cursive words. One valuable aspect of being able to enter handwriting into a computing device is that the written words can be recognized as text, after which the text can be searched, presented and edited by a text-editing program, and so forth.
One feature on some devices that is provided to users is that entered characters and words are able to be scratched out. Unlike ink on paper, the ink input system automatically removes scratched-out characters and words that the user deems should be removed. To this end, contemporary devices are configured to detect a scratch-out gesture, which is basically a particular symbol drawn on a tablet screen “through” the scratched-out word or character, or a particular movement made with a tablet pen, that erases ink.
Existing scratch-out gesture recognition systems are based on neural networks, and suffer from some significant usability problems. A main cause of the problems results from requiring a generally (and typically horizontally elongated) Z-shaped gesture. The neural net recognizer has stringent requirements for what constitutes a scratch-out gesture, which cause a relatively high rate of false negatives (e.g., the user wants to scratch-out some ink, but instead the gesture is recognized as an ink stroke). The gesture requirements also unnaturally limit the user in that the required scratch-out gesture is not something users will inherently discover; typical users may attempt some form of scratch-out gesture, however the Z-shaped gesture is neither intuitive nor natural to most users.
What is needed is a more natural scratch-out gesture (or set of gestures) that works with most users' personal styles of crossing out text. Any such scratch-out gesture should be intuitive for users as well as inherently discoverable, and generally should increase user satisfaction with hand-entered deletion operations. At the same time, the rate of correctly differentiating scratch-out gestures from other ink input should be improved.